Funds for a flow microfluorimeter/cell sorter are being requested. This instrument will be mainly used to support investigations of individuals holding NIH peer-reviewed grants. The machine will be used both for analysis and for sorting of single cells based upon size and/or natural or applied fluorescent material(s). Areas of investigation include the properties and distribution of bilirubin and BSP binding proteins in rat liver, studies of leukemogenesis in murine models as well as extensions of these investigations to human patients, identification of subpopulations and functions of immune system blood cells in leukemic and immunodeficient patients, synthesis and secretion of HBVsAg in hepatocellular carcinoma cell lines, mapping of individual human chromosomes in patients with inherited metabolic disorders, the cellular basis for erythropoiesis and hemoglobin function, examination of maternal blood for the prenatal diagnosis of genetic disorders, molecular control of differentiation of human and murine leukemic cells, the role of cell-cell interaction in the regulation of human adult and fetal hemoglobin synthesis, characterization of human skin Langerhans cells, viral induction of insulin dependent diabetes mellitus, the effects of histocompatible or incompatible platelete transfusions upon platelet transfusion therapy requirements, effect of carcinoma on normal tissues, development of brain cells in a rat model of phenylketonuria, and pharmacologic and cell cycle effects of phase I chemotherapeutic agents in vivo and vitro. Approximately a third of the purchase price will be furnished by the Mount Sinai School of Medicine, and up to 25T of th machine time will be used by investigators not NIH supported. The principal investigator and a Committee of Users will recruit an operator for the machine and have already begun establishing priorities for its use. Funding has been assured for the operator and supplies for the useful life of the machine. The users have identified present experiments which can be better performed using this machine and new avenues of investigation which will be opened.